Condition Mon Oil

7/31/2019 Condition Mon Oil

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CONDITION MONITORIN

TRANSFORMER OIL


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Parameters for condition monitoring of oil service

Two ways are available to an operating enginee1. To make periodic oil tests to establish trends an

them.

2. To conduct dissolved gas analysis to assess the

condition of transformers

PARAMETERS TO BE CHECKED ARE:

1. FLASH POINT

2. DIELECTRIC DISSIPATION FACTOR

3. SPECIFIC RESISTANCE

4. NEUTRALISATION.

5. MOISTURE CONTENT6. SLUDGE %

7. BREAK DOWN VOLTAGE

8. D.G.A.


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PHYSICAL CONTAMINATION

1. Dust, fibre, metallic, particles, other solid impu

2. Dissolution of varnish.

3. Free and dissolved water.

CHEMICAL DETERIORATION

Oxidation resulting in acids sludges and pimpurities.

CONTAMINATION OF GASES

a) Dissolved air from atm. Nitrogen, co

b) Generated in oil, methane, ethane, a

ethylene etc.Before the oil is put in

transformer, its properties should b

ensured.


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CHEMICAL DECOMPOSITION OF

HYDROCARBONS

Catalyst

RH R* + H

(Hydrocarbon) (Free radical

R* + O RO

(Peroxy radic

RO2* + RH RO2*H+ R

(Hydro per o


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2 RO2*

R* + RO2*

2 R*

Oxidation prod

(Higher TempeIons as catalys

the reaction)

Hydrocarbon RH first produces a free radical R. T

now combines with the available oxygen giving pe

First product of oxidation peroxides reacts with any

(RH) giving hydro peroxide RO2H and another fre

this type of chain propagation continues till thebroken adding suitable inhibitor.


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SERVICE OIL TESTS

The service oil tests to be conducted are furnished

Service oil tests as per IS: 1866 2000

Sl. No. TESTSINFORMATION PRO

TESTS1

Interfacial Tension Sludge present in the oil

2Neutralisation Number Acid present in the oil

3Moisture content (ppm)

Reveals total water cont

cellulosic deterioration.

4Flash point

Sudden drop in flash poiunsatisfactory working c

transformer.

5 Sludge Indicated deterioration


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6Dielectric Dissipation

Factor

Reveals presence of mo

varnishes or their produ

in oil

7 Dielectric strengthConductive contaminan

present in the oil.

8 Resistivity Indicative of conductin

9 Dissolved Gas Analysis

Reveals ppm of combu

dissolved in the oil to a

condition of the transfo


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A Typical Method to Maintain Test Record for T

TRANSFORMER DATA OIL DA

Location Oil supplierManufactures Name Code Designation

Manufactures Number. Inhibited or

Un-inhibited

Users reference

Number of phases. Type of Inhibitor

If present

Voltage Ratio

Outdoor or Indoor.

Type of cooling. Quantity of oil in

The system

With or without Conservator

Type of Breather


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INSTALLATION DATA

Filled on.

Commissioned on..

Maximum load...

Maximum oil temperature..

Normal load

Normal Oil Temperature


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MAINTENANCE OF DATA

1. Date of sampling..

2. Topping up done up.

Type and quantity of oil added

3. Note on abnormal operations...

4. Oil filtered on...5. Breather reconditioned on

6. Physical observation


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7. Tests conducted:

a. Interfacial Tension.

b. Neutralisation Number

c. Moisture content (ppm)

d. Flash point

e. Sludgef. Dielectric Dissipation Factor

g. Dielectric Strength

h. Resistivity


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TABLE 1: APPLICATION AND INTERPRE

TESTS ON OIL IN TRANSFORMERS

AS PER IS: 1866 1983

Sl.

N

o.

CharacteristicEquipment

voltage

Permissible

limit,

satisfactory for

use

1 Specificresistance at

90 c ohm-

cm, min

All

voltages0.1 * e12

2

Dielectric

dissipationfactor at 90 c,

max

> 145 kv< 145 kv

0.21.0


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Sl.

NoCharacteristic

Equipment

voltage

Permissible limit,

satisfactory for use

3

Neutralization

value,

mg / KOH / g

All

voltages0.5

4Precipitate

sludge

All

voltages

No perceptible

sludge

5 Flash pointAll

voltages

Decrease in flash

point 15c (max) of

the initial value,minimum value

125 c


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Sl.

N

o

CharacteristicEquipment

voltage

Permissible

limit,

satisfactory foruse

6

Interfacial

tension at

27c, n/m,

min

All

voltages0.015

7Electric

strength

145 kv +

above

< 145 kv

> 72.5 kv

< 72.5 kv

50kv min

40 kv min

40 kv min

30 kv min

8Water

content ppm

> 145 kv

< 145 kv

25 ppm

35 ppm


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LIMITING VALUES IS: 186

Test Equ. Voltage Method

Electric strength

> 145 kv

< 145 > 72.5

kv< 72.5 kvIs: 6792

Water content

ppm, max

> 145 kv

< 145 kv Is: 335

Specific

resistance @ 90,10 E12 ohm, cm All voltage Is: 6103

Tan delta @90,

max

> 145 kv

< 145 kvIs: 6262


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ACIDITY mg

KOH / g, Max

ALL

VOLTAGEIS: 1448

IFT, N/m. MinALL

VOLTAGEIS: 6104

FLASH POINT

Deg C, Min

ALL

VOLTAGE

IS: 1448

Max Dec 15

SEDIMENT

AND / OR

PRECIPITABLESLUDGE

ALL

VOLTAGE

IS: 1866

FOR TRANSFORMERS IN SERVICE


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Properties Condition Reme

Breakdown

voltageLow

Filtration und

+ temperatureMoisture High

Dielectric

dissipation

factor

HighFiltration as a

cause is moisVolume

resistivity Low

IFT Low Reclamation

GENERAL


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NV HIGH

FP LOWINVESTIGATE T

CAUSE

SLUDGE % HIGH DE-SLUDGING


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SUGGESTED LIMITS FOR IN SERVICE OILS GROUP I BY

BASED ON IS: 1866-1983

LIMITS_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

VOLTAGE CLASS

PROPERTIES

145 KV & 72.5 KV

ABOVE & < 145KV

ELECTRIC STRENGTH 50 40

(MIN) (MIN)

NEUTRALISATION VALUE 0.1 0.1

(mgKOH/g) (MAX) (MAX)

INTERFACIAL TENSION N/m 0.015 0.015

(MIN) (MIN)

DIELECTRIC DISSIPATION 0.2 1.0

FACTOR AT 90 C (MAX) (MAX)

WATER CONTENT, ppm 25 35

(MAX) (MAX)

SPECIFIC RESISTANCE

Ohm-cm 0.1x1012 0.1x1012


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Suggested limits for in service oils group ii by

(reconditioning) based on

IS: 1866-1983

LIMITSVOLTAGE CLASS

PROPERTIES - - - - - - - - - - - - - - - - - - - - - - - - -

145 KV & 72.5 KV

ABOVE & < 145KV

Electric strength < 50 < 40

Neutralisation 0.1 0.1

Value (mg.KOH/g) UPTO 0.5 UPTO 0.5

Interfacial < 0.015 < 0.015

Tension N/m (MIN) (MIN)

Dielectric dissipation > 0.2 > 1.0

Factor At 90 C

Water Content, ppm > 25 > 35

Specific resistance < 0.1 x1012 < 0.1 x1012

Ohm-cm


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TABLE IV

Suggested values for in-service oils group II by volta

(reconditioning) based on IS: 1866 (1983)

LIMITS

Voltage C

Properties

145 Kv & 72.5 Kv

Above & < 145kv

Electric Strength < 50 < 40

Neutralisation Value 0.1 0.1

(mg KOH/g) Upto 0.5 Upto 0.5

Interfacial Tension < 0.015 < 0.015

N/m

Dielectric Dissipation > 0.2 > 1.0

Factor at 90 C

Water Content, ppm > 25 > 35

Specific Resistance < 0.1 < 0.1

Ohm-Cm


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GROUP III OILS:

To categorize under group III, the paramete

well beyond the limits proposed in table IV

should be initially filtered under vacuum an

to verify whether the properties improve or

properties like Dielectric Dissipation Facto

Tension do not improve on filtration, then t

for oil to be replaced.


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Properties of oils evaluated in transformer

Sl.No Voltageclass BDV Tan Delta Resistivity

1 33 / 11 18 0.0321 0.914E12

2 66 / 11 38 0.0392 0.046E12

4 220 / 11 27 0.0108 2.75E12

5 220 / 11 35 0.263 0.912E12


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Properties of oils evaluated in transformer

Sl.

No

Voltage

class BDV

Tan

Delta Resistivity I

16 220 / 66 45 0.0032 6E12

17 66 / 11 47 0.0063 5.86E12

18 66 / 11 11 0.014 2.68E12

19 66 / 11 8 0.039 2.18E12

20 66 / 11 24 0.023 1.76E12


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Properties of oils evaluated in transfor

utility oil to be replaced/reclaim

Capacity

in MVA

Voltage in

KV BDV

Tan

Delta Resistivity

533 / 11 29 1.000 0.0177

533 / 11

-1.050 0.0151

5 110 / 33 /

11

-0.820 0.0194

533 / 11 24 0.270 0.0643

533 / 11 29 1.050 0.0168

533 / 11 37 0.720 2.3700

533 / 11 44 1.170 0.0150


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Properties of oils evaluated in transfor

utility oil to be replaced/reclaim

Capacityin MVA Voltage inKV BDV TanDeltaResistivity

5 33 / 11 44 0.990 0.0175

5 33 / 11 30 0.370 0.0452

5 33 / 11 39 0.290 0.0589

5 33 / 11 33 0.190 0.0905

5 33 / 11 29 0.680 0.0227

C


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5 33 / 11 63 0.880 0.0187

5 33 / 11 27 0.775 0.0222

5 33 / 11 22 1.100 0.0157

5 33 / 11 18 0.620 0.0283

5 33 / 11 15 0.700 0.0243


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CONCLUSIONS

a. In view of the importance of service oil tests, al

be carried out as per IS: 1866 systematically andas a part of maintenance schedule, as no single t

indicator.

b. The periodic testing will help O & M personnel

databank and case histories of power Transform

c. Periodic testing will help to know the oil condit

know growing of any incipient faults by Dissolv

Analysis.

d. The preventive maintenance followed by all util

not only savings in O & M costs but also prevenpremature breakdown / Failures besides improv

system reliability.


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Test required to assess the level of oil degrad

Screening tests: - Laboratory evaluation can be m

performing screening tests at site.

The tests are:

1. Appearance

i. Colour

ii. Visible particlesiii. Haziness or cloudiness

2. Acidity by colour

CPRI acidity testing kit

3. Interfacial tension test

By field method

4. Quality index

By Myers method


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PORTABLE ACIDITY TESTING KIT

A portable acidity testing kit was developed by cpri

check the acidity of transformer oil at site

Procedure:

A) 1.1 ml of oil in a test tube.

B) Add 1ml of rectified spirit.

C) Shake well

D) Add 1 ml. of alkaline solution

E) Add few drops of universal indicator

F) Match the colour with the colour chart to arrive a

value.

Advantages: Test can be performed by semi skilled p

the site of transformer / remote areas.


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SHAPES OF SPOTS

OIL ALONE INDICATOR

NEW OIL + INDICATOR SERVICE OIL

SHAPES OF INDICATOR SPOT ARE DEPENDENT ON


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Recommended limits of unused mineral oil fil

power transformer

Property Highest voltage equipmen


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Water content, ppm, min 20 15

Interfacial tension, N/m, min 35 35

Dielectric Dissipation Factor

@ 90 C, 40-60 Hz, max0.015 0.015

Resistivity, ohm-cm, min 6 6

Breakdown voltage, kV, min 40 50

Oxidation stability of

uninhibited oil

Neutralisation value,

Mg.KOH/g, min

Sludge (% by Mass), max

oxidation stability of inhibited

oil - induction period

0.4 0.4

0.1 0.1

Similar values before fill


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Condition Mon Oil

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